Carbon-based materials are considered as having a great potential to improve radio-frequency (RF) and even THz-frequency electronics as well as digital electronics. Graphene is a name given to a single layer of carbon atoms arranged in a honeycomb lattice, although also films built of few graphene sheets stacked one upon another are often referred to as graphene (or few-layer graphene) and shall also be considered as embodiments of a graphene layer herein. Single-layer graphene is a zero band gap semiconductor with outstanding material properties, such as charge carrier mobility of around 1.2×105 cm2/Vs at 240 K, high field electron velocity of 4×107 cm/s, sheet resistance as low as 125 Ω/sq (about 30 Ω/sq for four-layer films), and thickness of only 0.34 nm.
The document EP 2 525 409 discloses a graphene base transistor device having a graphene base for the transport of electrons into a collector. The transistor has a heterostructure comprising an emitter, a collector, and a graphene base layer of one or more sheets of graphene between the emitter and the collector. Graphene base transistors are sometimes also referred to as graphene junction transistors or as graphene hot electron or graphene hot-carrier transistors.